1. Field of the Invention
The present invention relates to printing devices, and particularly to a pagewidth inkjet printer that provides for simultaneous printing across a horizontal portion of a sheet of paper, as opposed to the horizontal scanning of a conventional inkjet printer.
2. Description of the Related Art
Inkjet printers are well known in the art. FIG. 2 is a schematic structural diagram of a printing system equipped with a conventional prior art inkjet printer 20. The printer 20 is equipped with a main scan feeding mechanism that slides carriage 30 back and forth along sliding axis 34 using carriage motor 24, a sub-scan feeding mechanism that transports printing paper P in a direction perpendicular to the main scan direction (called “the sub-scan direction”) using paper feed motor 22, a head driving mechanism that drives printing head unit 60, which is on carriage 30, and controls ink ejection and dot formation, and control circuit 40, which exchanges the control signals with these paper feed motor 22, carriage motor 24, printing head unit 60, and operating panel 32. Control circuit 40 is connected to computer 88 via connector 56.
The main scanning mechanism for reciprocating the carriage 30 includes a sliding shaft 34 mounted on the platen 26 and designed to slidably support the carriage 30, a pulley 38 for extending an endless drive belt 36 between the carriage 30 and the carriage motor 24, and a position sensor 39 for sensing the origin position of the carriage 30. Typically, the sub-scanning mechanism for transporting the printing paper P is provided with a gear train (not shown) for transmitting the rotation of the paper feed motor 22 to a paper feed roller (not shown). The paper feed roller transports the printing paper in the direction perpendicular to the sliding direction of the carriage 30.
FIG. 4 is a block diagram illustrating the structure of prior art inkjet printer 20 with control circuit 40 as its core. Control circuit 40 is formed as an arithmetic logical operation circuit having a CPU 41, programmable ROM (PROM) 43, RAM 44, and a character generator (CG) 45 that records the dot matrix of characters. This control circuit 40 further includes a dedicated interface circuit 50 that performs an interface exclusively with an external motor, a head drive circuit 52 that is connected to this dedicated interface circuit 50, drives the printing head unit 60, and ejects ink, and a motor drive circuit 54 that drives paper feed motor 22 and carriage motor 24. Dedicated interface circuit 50 has a built in parallel interface circuit, and can receive printing signal PS supplied from computer 88 via connector 56. By executing the computer program stored in PROM 42, CPU 41 functions as the color mode unit 41a, monochromatic mode unit 41b and position adjusting feed unit 41c. An upper-edge color mode is performed by the upper-edge unit 41a1 of the color mode unit 41a, whereas the routine color mode is performed by a routine unit 41a2. Color mode printing based on routine feeding is performed with the aid of the routine unit 41a2 of the color mode unit 41a, whereas color mode printing based on minor feeding is performed by a lower-edge unit 41a3. Similarly, upper-edge monochromatic mode printing is performed by the upper-edge unit 41b1 of the monochromatic mode unit 41b, whereas routine monochromatic mode printing is performed by a routine unit 41b2. The monochromatic mode printing based on routine feeding is performed with the aid of the routine unit 41b2 of the monochromatic mode unit 41b, whereas the monochromatic mode printing based on minor feeding is performed by a lower-edge unit 41b3.
As best shown in FIG. 3, printing head 28 has a plurality of nozzles n provided in a row for each color, and an actuator circuit 90 that operates a piezo-element PE that is provided on each nozzle n. Actuator circuit 90 is part of head drive circuit 52 (see FIG. 4), and performs on/off control of drive signals given from a drive signal generating circuit (not illustrated) within head drive circuit 52. Specifically, actuator circuit 90 latches data that shows “on” (i.e., when ink is ejected) or “off” (i.e., when ink is not ejected) for each nozzle according to the print signal PS supplied from computer 88, and the drive signal is applied to the piezo-element PE only for the nozzles that are on.
FIG. 3 illustrates the arrangement of nozzles provided on printing head 28. The conventional prior art inkjet printer 20 is a printing apparatus that performs printing using four colors of ink: black (K), cyan (C), magenta (M), and yellow (Y). Five nozzles each are provided for cyan (C), magenta (M), and yellow (Y), and fifteen nozzles are provided for black (K). The cyan nozzle group, magenta nozzle group, and yellow nozzle group are arranged in sequence in the direction of sub-scanning. The black nozzle group is disposed in the area for accommodating the nozzles of the cyan nozzle group, single chromatic nozzle group, and yellow nozzle group in the direction of sub-scanning. Nozzles #1 through #5 of cyan (C), magenta (M) and yellow (Y) correlate to a “single chromatic nozzle group”. Nozzles #1 through #15 for black (K) correlate to an “achromatic nozzle group”.
Provided in actuator circuit 90 are actuator chips 91 to 93 which drive black nozzle row K, actuator chip 94 which drives cyan nozzle row C, actuator chip 95 which drives magenta nozzle row M, and actuator chip 96 which drives yellow nozzle row Y. In use, printing head 28 slides back and forth along sliding axis 34 in the direction of arrow MS (in FIG. 3) by carriage motor 24. Printing paper P is sent in the arrow SS direction in relation to printing head 28 by paper feed motor 22.
Conventional inkjet printers, such as the printer 20 described above, contain moving assemblies, thus often causing the printing process to be relatively slow, as well as requiring frequent calibration and being prone to misalignments, mechanical damage and other malfunctions.
Thus, a pagewidth inkjet printer solving the aforementioned problems is desired.